Shahnaz ('Shaz') Hoque
Fighting climate change with a star in a box!
My parents emigrated from a village in Bangladesh to London, where I was born. I grew up on a council estate there and went to a school where we had one teacher for every subject. My parents divorced, so I moved with my mum and changed schools, while my dad and brother moved to Qatar.
I always loved school because I could keep learning things constantly while everything else in my life changed. Because of this, in secondary school I loved every subject. However, it was in science that I never ran out of questions and curiosity. I learnt about nuclear fusion then and immediately knew it was something I wanted to be part of.
Left to right: Me at four years old; with my older brother Sami - who is a pharmacist - and my mother in Bangladesh, where I lived from six months to one year old.
I worked hard to get the top GCSE grades at school, a bursary to study at a top private school for free to do my A-levels, and a place to study for a Masters in Nuclear Engineering at the University of Birmingham, where I was the only woman on my course. I loved my degree, because I was finally able to learn what I needed to help fight climate change in the best way I thought. I was the only Black, Asian and Minority Ethnic (BAME) woman on my course in its first year of existence, making me one of the first BAME women with an undergraduate Masters in Nuclear Engineering in the UK.
Left - doing my Masters; right - a photo of me on the last day of my job as a Nuclear Engineer in Bristol. The balloon says ‘Future Fusion Doctor.’
After university, I worked in the nuclear industry alongside a few BAME female engineers to help build the first nuclear fission reactor in the UK for a generation, but I still dreamt about being part of the race for nuclear fusion. I left my job to do a PhD at the University of Oxford, investigating materials for nuclear fusion reactors and finally my dream has come true. I feel very privileged to be a BAME woman from a working class, immigrant family, raised by my mum alone and also at the best university in the world, able to follow my lifelong dream. I hope to help the next generation of BAME people in the UK who love anything in STEM to follow their dreams too, despite the difficulties we face as the minority here.
Left to right: At ITER; inside ITER; at MAST-U - hard hat required! ITER is going to be the largest nuclear fusion reactor in the world, being built in France. I dreamt about going there when I first learnt about nuclear fusion in school and doing this PhD allowed me the opportunity to finally go. MAST-U is a smaller fusion reactor on the same premises as JET and I got to visit during my PhD.
...on nuclear fusion
In the future, it is predicted that energy from nuclear fusion will power the world instead of fossil fuels. Fusion does not emit any greenhouse gases and the hydrogen fuel it uses is virtually limitless – helping us in the fight against climate change. Researchers have been searching for the best way to build a nuclear fusion reactor for generations.
What is nuclear fusion?
Nuclear fusion is when the non-pollutive gas hydrogen is heated up to approximately 150,000,000°C – ten times hotter than the centre of the Sun. The particles in it then have enough energy from the heat to fuse together and make helium gas – which rarely reacts with anything – and a neutron. The nuclear fusion reaction is the most energetic in the universe and what is happening in stars like the Sun.
Figure 1: What happens in a nuclear fusion reactor. Hydrogen is heated up and fuses to make helium and lots of neutrons, which fly out to the reactor walls in every direction1.
How do we get energy from fusion?
When hydrogen fuses, helium and a neutron are created. A neutron is an extremely small particle that is part of almost every atom of every element in the universe. After it is created from hydrogen fusion in the reactor core, it has lots of energy which propels it into the reactor walls. It hits the wall and transfers its energy to the materials inside. If a liquid (like water) is put in the walls through pipes, the water heats up using the energy from the millions of neutrons hitting it. The hot water is carried away as it transitions to steam, which turns a machine, generating electricity (much like a wind-turbine).
Figure 2: Inside the world's biggest fusion reactor, called JET. This is in Oxfordshire! The purple on the right shows when the hydrogen is almost hot enough for fusion to occur2. I visited as part of my undergraduate degree and now my PhD is part-funded by the organisation that run JET and I have a supervisor who works there.
There are no fossil fuels and very little highly radioactive nuclear fuel waste to worry about, unlike with nuclear fission reactors. Moreover, a very small amount of hydrogen (about a bathtub’s worth) can produce your entire life’s electricity needs! By building a fusion reactor on Earth, we can copy the Sun to give us clean and virtually unlimited energy for generations.
What do I do?
I investigate the effects of radiation on steel which will be used to build nuclear fusion reactors, to make them safer and longer lasting. My research helps develop fusion energy – a clean, safe and efficient way to produce electricity. I am trying to learn how the neutron from the reaction changes the structure of the steel used to build the reactor walls, so I can help other scientists and engineers design the best steels to use for building one.
The walls of a nuclear fusion reactor will be built from steel. They will be hit with millions of neutrons from the fusion reaction, which can change the structure of the steel so it has different properties. If you look at fusion steel under a very powerful microscope, you can see it is made of lots of particles of iron, chromium, carbon and many other elements, arranged in a crystal lattice.
Figure 3: Metals are crystal lattices, which look like this under a microscope. This picture shows a perfect lattice, where all of the particles in a metal are lined up together perfectly3.
When a fusion neutron with lots of energy hits the steel, it moves the particles out of their places, rearranging the crystal structure and creating defects called ‘dislocations.’ Dislocations are areas where the particles are out of their normal positions and can be a sign of radiation damage.
Figure 4: This is a diagram of a dislocation, which is created when the metal particles are out of their normal positions in a crystal lattice4.
Radiation damage affects a material’s properties
When you apply force to a metal like steel which has lots of dislocations in it from radiation damage, the dislocations move through the crystal lattice. When lots of dislocations move, the steel can crack and break. That’s why lots of dislocations can change the properties of the steel, making it more brittle (or easier to break) – which is not good for fusion reactor walls. I am trying to find the most accurate way of determining how dislocations from radiation damage move through steel. This will help other researchers to design steels that will have better properties for building a fusion reactor with (i.e. that will not break as easily!).
To investigate how dislocations move through steel, I use small steel samples in the shape of a dogbone. I irradiate these using a big machine called a ‘particle accelerator’. This machine fires my samples with particles called protons, which weigh exactly the same as neutrons but are charged so can be moved around using electromagnets.
Figure 5: Left - small dog bone-shaped steel sample; right - microtensile rig with a small steel sample fixed inside. The sample has been pulled to breaking.
I put the irradiated samples in a machine called a ‘microtensile’ rig, which tightly grips them and pulls them from both sides to stretch them. This applies force to the samples to move the dislocations through the steel crystal lattice. While the rig pulls, it sends information to a computer every 100th of a second about how much force it is applying.
A camera or microscope also takes images every 100th of a second during the test and sends these to the same computer. I can analyse the data from the images and the force readings to find out about the way the dislocations moved through the steel samples as they were being pulled.
Figure 6: Experimental setup of microtensile rig with a camera pointed at it to take photos of the steels samples as they are pulled.
Computer models predict how materials behave, which can help us design better fusion reactors with fewer experiments. A ‘crystal plasticity (CP)’ model contains lots of information that has already been discovered about how materials behave, including how dislocations move through steel. The CP model can only contain one of these theories at once, to predict the behaviour of a steel. A good way to find out which one to use is to compare the CP model with experimental results. I can use the data from my steel samples using the microtensile rig.
I will run a CP model with different theories of how dislocations move in steel and compare the results with my real experimental results. When the results are the closest match, I will know which theory is best for predicting how dislocations move through my steel. Future scientists can use that theory when they want to know how the steel they are investigating will behave in a fusion reactor.
Figure 7: Dalton Cumbria Facility for irradiating steel samples. A particle accelerator here fires protons at the samples at high speed.